When an electric vehicle equipped only with an electric motor as a drive source travels at low speed, the travelling sound emitted from the electric vehicle is very small. When a hybrid vehicle equipped with an electric motor and an internal-combustion engine as drive source travels at low speed, the travelling sound emitted from the hybrid vehicle is very small because only the electric motor is driven at the low-speed travelling. For this reason, a pedestrian may not notice the vehicle approaching.
A vehicle approach alert device is proposed for such low noise vehicle, by which a pedestrian outside the vehicle can notice the presence of vehicle due to a warning sound which notifies the approach of vehicle.
JP 5026536 B (corresponding to US 2011/0175718 A1) describes an equipment generating a beep sound from a speaker outside a vehicle in response to a standard signal in sync with rotation of a drive motor. Further, an output sound of a speaker inside the vehicle is controlled through an amplifier such that a microphone located at a position where the sound is to be reduced inside the vehicle receives the minimum input.
JP 3257012 B describes an equipment generating a beep sound from a speaker outside a vehicle. Further, a canceling sound is generated inside the vehicle to cancel the beep sound transmitted to the inside from the outside of the vehicle. The canceling sound is output from a speaker inside the vehicle.
However, in JP 5026536 B and JP 3257012 B, it is necessary for a control part to execute real time calculation based on the input from a microphone every time in consideration of a signal for outputting a beep sound to cancel the warning sound. For this reason, the control part needs to perform complicated processing, and the processing load of the control part is large.